Fluorescent manganese-doped zinc sulphide nanoparticles for spectral shifting

Spectral shifting by luminescent nanoparticles is expected to enhance solar cell performance by avoiding wastage of high energy photons. Manganese-doped zinc sulphide nanoparticles, with a PL emission peak around 600 nm, were selected as a possible candidate for such a luminescent down-shifting material. To investigate their fluorescence properties, ZnS:Mn nanoparticles were synthesized by a chemical route using thiourea to limit the reaction rate and achieve controlled, uniform formation of nanoparticles. Incipient ZnS:Mn nanoparticles were encapsulated in ZnS shells by employing the in-situ thermal decomposition of pre-formed zinc-thiourea complex. The resulting core-shell nanoparticles were dispersed in a protective matrix composed of sodium hexametaphosphate. TEM studies showed the formation of spherical and distinct ZnS:Mn nanoparticles in the size range 50-100 nm, while UV-Vis spectra clearly showed quantum confinement effects.